Effect of ethanol on calcium metabolism was studied in several experimental preparations. These include presynaptic nerve terminals (synaptosomes), synaptosomal plasma membranes (SPM), and the mitochondrial pellet isolated from rat brain and synaptosomal plasma membranes as well as erythrocyte ghosts isolated from ethanol treated rats. The intracellular calcium metabolism in synaptosomes was studied with the fluorescent probe Rhodamine 6 G. A metallochromic calcium indicator dye, arsenazo III (Az) was employed to detect micromolar changes in extracellular calcium ion concentrations. The radioactive calcium (Ca-45) was used to measure the calcium levels in synaptosomes and in erythrocyte ghosts. Terbium fluorescence was used to probe membrane calcium interaction, and chlortetracycline (CTC) fluorescence was used to monitor the membrane bound calcium during ethanol dependence. Ethanol (20-200 mM) was found to increase calcium-45 binding to SPM and decrease binding to the mitochondrial pellet. In synaptosomes, addition of ethanol (10-200 mM) caused release of calcium from intracellular sites as measured by (Ca-Az) absorbance. Long term ethanol treatment increased (Ca-45) calcium binding in synaptosomal plasma membranes. These results suggest that ethanol affects calcium metabolism in neuronal tissue. This information could provide an experimental basis for investigating the molecular basis of neurological and behavioral changes due to ethanol intoxication.